Change search
ReferencesLink to record
Permanent link

Direct link
Potential of Ventilation Radiators: Performance evaluation by numerical, analytical and experimental means
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Fluid and Climate Technology.
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Energy consumption for heating and ventilation of buildings is still in 2011considered far too high, but there are many ways to save energy and construct lowenergy buildings that have not been fully utilised. This doctoral thesis has focused onone of these - low temperature heating systems. Particular attention has been given tothe ventilation radiator adapted for exhaust-ventilated buildings because of itspotential as a low energy consuming, easily-operated, environmentally-friendlysystem that might also ensure occupant health and well-being.

Investigations were based on Computational Fluid Dynamics (CFD) simulations andanalytical calculations, with laboratory experiments used for validation.

Main conclusions:

  • Low and very low temperature heating systems, such as floor heating, in general createan indoor climate with low air speeds and low temperature differences in the room, whichis beneficial for thermal comfort. A typical disadvantage, however, was found to beweakness in counteracting cold down-flow from ventilation air supply units in exhaustventilatedbuildings.
  • with ventilation radiators, unlike most other low temperature systems, it was found thatthe risk of cold draught could be reduced while still maintaining a high ventilation rateeven in cold northern European winters.
  • ventilation radiators were found to be more thermally efficient than traditional radiators.
  • design of ventilation radiators could be further modified for improved thermal efficiency.
  • at an outdoor temperature of -15 °C the most efficient models were able to give doublethe heat output of traditional radiators. Also, by substituting the most efficient ventilationradiators for traditional radiators operating at 55 °C supply water temperature, it wasfound that supply water temperature could be reduced to 35 °C while heat outputremained the same and comfort criteria were met.
  • lowering the supply water temperature by 20 °C (as described above) could givecombined energy savings for heating and ventilation of 14-30 % in a system utilising aheat pump.
  • supply water temperatures as low as 35 °C could increase potential for utilising lowtemperature heat sources such as sun-, ground-, water- or waste-heat. This would beparticularly relevant to new-built “green” energy-efficient buildings, but severaladvantages may apply to retrofit applications as well.
  • Successful application of ventilation radiators requires understanding of relevant buildingfactors, and the appropriate number, positioning and size of radiators for best effect.Evaluation studies must be made at the level of the building as a whole, not just for theheating-ventilation system.

This work demonstrated that increased use of well-designed ventilation radiatorarrangements can help to meet regulations issued in 2008 by the Swedish Departmentof Housing (Boverket BBR 16) and goals set in the Energy Performance of BuildingsDirective (EPBD) in the same year.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology , 2011. , 63 p.
Keyword [en]
Ventilation radiator, thermal comfort, exhaust ventilation, CFD, energy saving, convection fin, low temperature heating
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-31813ISBN: 978-91-7415-940-0OAI: oai:DiVA.org:kth-31813DiVA: diva2:406505
Public defence
2011-04-18, F3 (Flodis), Lindstedtsvägen 26,, 114 28 Stockholm, 16:12 (English)
Opponent
Supervisors
Projects
STEM Projektnummer:30326-1 Energieffektiva lågtemperatursystem i byggnader
Note
QC 20110328Available from: 2011-03-29 Created: 2011-03-25 Last updated: 2011-04-05Bibliographically approved
List of papers
1. Flow patterns and thermal comfort in a room with panel, floor and wall heating
Open this publication in new window or tab >>Flow patterns and thermal comfort in a room with panel, floor and wall heating
2008 (English)In: Energy and Buildings, ISSN 0378-7788, Vol. 40, no 4, 524-536 p.Article in journal (Refereed) Published
Abstract [en]

Thermal comfort aspects in a room vary with different space heating methods. The main focus in this study was how different heating systems and their position affect the indoor climate in an exhaust-ventilated office under Swedish winter conditions. The heat emitters used were a high and a medium-high temperature radiator, a floor heating system and large wall heating surfaces at low temperature. Computational fluid dynamics (CFD) simulations were used to investigate possible cold draught problems, differences in vertical temperature gradients, air speed levels and energy consumption. Two office rooms with different ventilation systems and heating needs were evaluated. Both systems had high air exchange rates and cold infiltration air.

The general conclusions from this study were that low temperature heating systems may improve indoor climate, giving lower air speeds and lower temperature differences in the room than a conventional high temperature radiator system. The disadvantage with low temperature systems is a weakness in counteracting cold down-flow from ventilation supply units. For that reason the location of heat emitters and the design of ventilation systems proved to be of particular importance. Measurements performed in a test chamber were used to validate the results from the CFD simulations.

Keyword
thermal comfort, energy consumption, exhaust ventilation, CFD simulations
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-8213 (URN)10.1016/j.enbuild.2007.04.011 (DOI)000252789000014 ()2-s2.0-37349005232 (ScopusID)
Note
QC 20101118 Uppdaterad från accepted till published (20101118).Available from: 2008-04-09 Created: 2008-04-09 Last updated: 2011-03-29Bibliographically approved
2. Design considerations with ventilation-radiators: Comparisons to traditional two-panel radiators
Open this publication in new window or tab >>Design considerations with ventilation-radiators: Comparisons to traditional two-panel radiators
2009 (English)In: Energy and Buildings, ISSN 0378-7788, Vol. 41, no 1, 92-100 p.Article in journal (Refereed) Published
Abstract [en]

Performance of heat emitters in a room is affected by their interaction with the ventilation system. A radiator gives more heat output with increased air flow along its heat transferring surface, and with increased thermal difference to surrounding air. Radiator heat output and comfort temperatures in a small one-person office were Studied using different positions for the ventilation air inlet. In two of the four test cases the air inlet was placed between radiator panels to form ventilation-radiator systems. Investigations were made by CFD (Computational Fluid Dynamics) simulations, and included visualisation of thermal comfort conditions, as well as radiator heat output comparisons. The room model was exhaust-ventilated, with an air exchange rate equal to what is recommended for Swedish offices (71 s(-1) per person) and cold infiltration air (-5 degrees C) typical of a winter day in Stockholm. Results showed that under these conditions ventilation-radiators were able to create a more stable thermal climate than the traditional radiator ventilation arrangements. In addition, when using ventilation-radiators the desired thermal climate could be achieved with a radiator surface temperature as Much as 7.8 degrees C lower. It was concluded that in exhaust-ventilated office rooms, ventilation-radiators can provide energy and environmental savings.

Keyword
Ventilation-radiator, Exhaust ventilation, CFD simulation, Thermal, comfort, Energy consumption, Low temperature heating
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-18031 (URN)10.1016/j.enbuild.2008.07.014 (DOI)000261483800011 ()2-s2.0-55649110025 (ScopusID)
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2013-04-30Bibliographically approved
3. Improving the thermal performance of ventilation radiators: The role of internal convection fins
Open this publication in new window or tab >>Improving the thermal performance of ventilation radiators: The role of internal convection fins
2011 (English)In: International journal of thermal sciences, ISSN 1290-0729, Vol. 50, no 2, 115-123 p.Article in journal (Refereed) Published
Abstract [en]

This paper deals with heat output optimization of a ventilation radiator by varying the distribution of vertical longitudinal convection fins. A ventilation radiator, which combines ventilation air supply and heat emission to the room, has a higher driving force on air in between the radiator panels compared to traditional radiators and can for this reason have more heat transferring surfaces to improve thermal efficiency. Improving the thermal efficiency means a lower water temperature is required for heating and energy can be saved in production and distribution of heat in systems with heat pumps, district heating or similar. The investigation was made using Computational Fluid Dynamics (CFD) simulations while analytical calculations were used for verification of different flow and heat transfer mechanisms. Results showed that heat transfer can be increased in the section where ventilation air is brought into the room by slightly changing the geometry of the fins, decreasing the fin to fin distance and cutting off a middle section of the fin array. This change in internal design could mean considerable increase in thermal efficiency for the ventilation radiator as a whole.

Keyword
Ventilation radiator, Convection fins, CFD simulation, Exhaust ventilation, Thermal comfort, Energy consumption, Low-temperature heating
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:kth:diva-30542 (URN)10.1016/j.ijthermalsci.2010.10.011 (DOI)000286082300001 ()2-s2.0-78649639757 (ScopusID)
Note
QC 20110303Available from: 2011-03-03 Created: 2011-02-28 Last updated: 2011-03-29Bibliographically approved
4. Performance evaluation of ventilation radiators
Open this publication in new window or tab >>Performance evaluation of ventilation radiators
2010 (English)In: International journal of thermal sciences, ISSN 1290-0729Article in journal (Refereed) Submitted
Keyword
Ventilation radiator, Convection fins, CFD simulation, Exhaust ventilation, Thermal comfort, Energy consumption, Low-temperature heating
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:kth:diva-31935 (URN)
Note
QS 20120315Available from: 2011-03-29 Created: 2011-03-29 Last updated: 2012-03-15Bibliographically approved
5. Comfort temperatures and operative temperatures in an office with different heating methods
Open this publication in new window or tab >>Comfort temperatures and operative temperatures in an office with different heating methods
2006 (English)In: Proceedings of the Healthy Buildings Conference: Vol. 2: Indoor Climate, 2006, Vol. 2, 47-52 p.Conference paper (Other academic)
Keyword
Computational Fluid Dynamics, Low temperature heating, Comfort temperature, Operative temperature, Radiation asymmetry
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-8215 (URN)2-s2.0-84871575806 (ScopusID)
Note
QC 20101118Available from: 2008-04-09 Created: 2008-04-09 Last updated: 2011-03-29Bibliographically approved
6. Summertime cooling with ventilation radiators
Open this publication in new window or tab >>Summertime cooling with ventilation radiators
2007 (English)In: IAQVEC 2007 Proceedings - 6th International Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings: Sustainable Built Environment, 2007, 533-538 p.Conference paper (Refereed)
Abstract [en]

Ventilation radiators, heat emitters where cold ventilation air is brought directly from outdoors into the room via heated radiator surfaces, are becoming more and more common in Scandinavia. Because these systems combine both heating and ventilation several interesting aspects arise that may be used to save energy and improve indoor thermal climate. The heating aspects in wintertime have been discussed in previous papers from KTH STH. This study investigates whether ventilation radiators may be used for cooling in summertime. Results from the study show that condensation of water is the main problem to tackle when ventilation radiators are used for cooling purposes. It is difficult to avoid condensation, especially inside the ventilation channel where incoming ventilation air comes into contact with chilled radiator surfaces. The problem increases with increased temperature difference between radiator surface and ventilation air. This is why ventilation radiators seem unsuitable for cooling in summertime without risking condensation of water. However, if condensation of water is allowed in the ventilation channel only, ventilation radiators may be functional for cooling. The trick is to find a way to drain water from the ventilation channel to avoid hygiene problems.

Keyword
Condensation, Summertime cooling, Ventilation radiator
National Category
Other Civil Engineering
Identifiers
urn:nbn:se:kth:diva-31936 (URN)2-s2.0-84857249147 (ScopusID)978-486163071-2 (ISBN)
Conference
The 6th International Conference on Indoor Air Quality, Ventilation & Energy Conservation in Buildings IAQVEC 2007, Oct. 28 - 31 2007, Sendai, Japan
Note

QC 20110328

Available from: 2011-03-29 Created: 2011-03-29 Last updated: 2014-10-27Bibliographically approved
7. Energy savings and thermal comfort with ventilation radiators: a dynamic heating and ventilation system
Open this publication in new window or tab >>Energy savings and thermal comfort with ventilation radiators: a dynamic heating and ventilation system
2007 (English)In: Proceedings of Clima 2007 WellBeing Indoors, 2007Conference paper (Other academic)
Abstract [en]

Studies indicate that a high ventilation rate with fresh air supply directly from outdoors gives better thermal comfort conditions, less SBS (Sick Building Syndrome) symptoms and increased work productivity. The drawbacks with a high ventilation rate in natural or exhaust ventilated buildings are normally increased energy use for heating and cold air draught. Such problems may be minimized with ventilation radiators, radiators where cold ventilation air is brought directly from outdoors through a wall channel into the radiator where it is heated before entering the room.

This paper discusses advantages with ventilation radiators in comparison to those of traditional heating systems. Focus has been on energy aspects and thermal comfort. The main conclusions are that ventilation radiators may give a stable and uniform thermal indoor climate. The high thermal gradient between cold ventilation air and the radiator surface inside the ventilation channel also makes the ventilation radiator more efficient than other systems. A method to vary indoor climate on a daily basis according to where people stay is proposed for additional energy savings with ventilation radiators. The deductions were based on results from CFD simulations in a well validated office model.

Keyword
Ventilation radiator, CFD, thermal comfort, energy consumption
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-8216 (URN)
Conference
Clima 2007, 10-14 June, Helsinki, Finland
Note
QC 20101118Available from: 2008-04-09 Created: 2008-04-09 Last updated: 2011-03-29Bibliographically approved

Open Access in DiVA

fulltext(1977 kB)2981 downloads
File information
File name FULLTEXT03.pdfFile size 1977 kBChecksum SHA-512
b8fd1dc6330696cb97bc32d58a55e8ec1aa65a14f743cb074c314fb446af5cea4ae715af1cb2ba96a9ff548c6188edb6a03ea2fdcfa43556830dc278f692cd1c
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Myhren, Jonn Are
By organisation
Fluid and Climate Technology
Building Technologies

Search outside of DiVA

GoogleGoogle Scholar
Total: 2991 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 659 hits
ReferencesLink to record
Permanent link

Direct link